Focal plane shutter for cameras



I March30,1943.' A IMMQ 2,315,279

FOCAL PLANE SHUTTER FOR CAMERAS Filed Aug 29, 1941 l -4 Sheets-Sheet l 04 Alfred 541mm",

A TTORNEY.

March 30, 194-3. A, s n 2,315,279

FOCAL PLANE SHUTTER FOR CAMERAS Filed Aug. 29, 1941 I 4 Sheets-Sheet 2 INVENTOR. fllfrcd Snvmwn Afmk/vEY- March 30, 1943. A. SIMMON FOCAL PLANE SHUTTER FOR CAMERAS Filed Aug. 29, 1941 4 Sheets-Sheet 5 ATTORNEY March so, 1943. A. SIMMON 2,315,279

' FOCAL PLANE SHUTTER FOR CAMERAS Filed Aug. 29, 1941 4 Sheets-Sheet 4 II-III I INVENTOR.

A TTORNE).

Patented Mar. 30, 1943 UNITED STATES PATENT OFFICE I rociin ruins $222; For. CAMERAS I Alfred Simmon, to Simmon Jackson Heights, N. 2., as-

Brothers Inc., Long Island City, N. Y., a corporation of New York Application August 29, 1941, Serial No. 408,798

18 Claims.

Existing focal plane shutters consist usually of two curtains which are wound or unwound on two or more reels. .The leading reel is driven by a,

spring and, by combining different spring tensions and slots of diflerent width between the two curtains, a wide range of exposure times may be ob tained. This type of shutter has the following principal objections:

It is diiiicult by simple means to expose the film uniformly. Since the shutter starts from zero velocity and becomes gradually accelerated by the spring, it will be clear that the last part of the film receives usually considerably less light than the part first exposedi Brakes and other undesirably complicatedexpedlents have been used to overcome this. but only with moderate success.

Further, it is not particularly easy to adjust the width of the slot since this involves commonly an adjustment of 'two curtains relative to each other. This is usually done by a train of gears orby differential drives or by other not particularly simple means. Moreover, special means must be employed to reset the shutter in such a way that the film is not again exposed, adding considerably to the complicated construction of the entire shutter.

It is the principal object of this invention to provide a focal plane shutter which can be operated at practically uniform speed.

Another object is to use in such a shutter, simple means, readily adjusted, for varying the width of the slit therein.

A further object is to make the shutter practically automatically resetting'by providing means for returning the shutter always to the same. position requiring only retensioning of a spring member.

A still further object is to accomplish the aforementioned advantages by extremely simple means,

they appear view taken along the plane looking in the direction of I the arrows and a few parts being omitted for the sake of cleamess;

Fig. 4 is afront elevational view of the shutter of Fig. 1', a portion ofthe operating handlebeing broken away; I

Fig. 5 is a diagrammatic view illustrative of the principle of operating of the shutter. and -show-. ing particularly the effect of separation of the reels on the width of the shutter slit; I

Figs. 6 and 'l are plan views of constructional details; I I

Fig. 8 is a fragmentary perspective view of the mechanism for operating the shutter, the showing being more or less diagrammatic;

Fig. 9 is aview, partly in section, along the plane of line 8-9 in Fig. 1, looking in the direction of the arrows, and portions being omitted for sake of clearness;

Fig. 10 is a plan view operating mechanism as they appear after operation of the shutter and before resetting the shutter, the upper portions of the shutter being shown in broken lines so as to expose the operating mechanism;

Fig. 11 is a plan view, similar to Fig. 1, showing the parts of the shutter operating mechanism as of setting the shutter, namely the operation of setting the trigger;

Fig. 12 is a fragmentary rear elevational view, corresponding to the lower right hand corner of Fig. 2, but showing the trigger in its set position easy to operate and most economical to manufacture. I I

Still other objects will become apparent after a perusal of the following specifications on hand of the accompanying drawings in which a preferred embodiment of the shutter and its operating mechanism are shown in a more or less diagrammatic manner.

In the drawings,

Fig. l is a plan view of my improved focal plane shutter, portions being broken away to disclose the underlying construction, and portions of a camera with which the shutter is associated being indicated in broken lines;

Fig. 2 is a rear elevational view of the shutter as it appears in Fig. 11, and p v Fig. 13 is a plan view similar to Fig. 11, but showing the parts of the shutter operating mechanism as they appear after" the second and final step in effecting the setting of the shutter, after which it is ready for the release which will bring the parts back into the position of Fig. 10.

Like characters of reference denote similar {parts throughout the several views and the following specification.

Before going into embodiment of the invention the salient thereof will be briefly enumerated. I

' Mounted in a suitable frame work area pair of reels, spaced from each other, on which is carried the shutter curtain in the form of an endfeatures less band having a slit formed therein through wh ch light from the lens isadmitted to the film.

similar to Fig. 1, but more or less diagrammatic of the parts of the shutter after the first stage in the operation the details of the illustrated Suitable mechanism is provided for giving a starting impulse or kick to the curtain, prior to exposure, which thereafter moves with the reels at substantially uniform speed through a complete cycle, at the end of which it has returned to its initial position, ready for the next operation.

In order to assist in obtaining the desired uniform speed of travel of the curtain, the curtain-carrying reels are journailed in bearings of a low friction type, such as ball bearings, and no brake or other device is used to retard the curtain. Thus when the curtain receives an impulse or kick'as before stated, prior to the exposure, the moving parts move freely during the exposure proper under their own momentum with slowly decreasing velocity. If friction were totally absent, the shutter would move during the exposure with truly constant velocity, but since at least a small amount of friction is always present, the velocity will in reality slowly decrease. If the amount of friction is small, as with bearings of the type explained above, the decrease will also be small and in this manner a uniform velocity will be obtained with a much better degree of approximation than possible heretofore.

To bring the shutter to a stop at the desired point, a simple form of stop is used. In order to permit of quick starting and stopping without undu strain, the curtain and the reels are made as light as possible consistent with other requirements.

The curtain consists of twc parts, the curtain proper, which will hereinafter be referred to as the curtain, and which is a sheet of opaque, flexible but not stretchable material, and elastic means connecting the free ends of this curtain in such a way as to form an endless belt, The free ends of the curtain are spaced so as to form a slit, and the width of this slit is adjustable because of the elastic connecting means, which always tends to reduce the width of the slit. This width is adjustable by varying the distance between the curtain-carrying reels.

The framework carrying the curtain and its reels is movable relative to the main body of the camera, which comprises a suitable housing within which the curtain as well as the film spools are positioned. The lens is carried on an extension of the housing, and a bellows or other type of light-proof enclosure extends between the housing and the lens.

The film spools are mounted in the housing, and the framework carrying the curtain, which is movable relative to the housing and therefore also to the film, carries a pressure plate, which during exposure is firmly clamped against the film to hold it flat, but is moved away from the film a short distance during the film winding op- 1 oration.

means for operating the trigger, means for adjusting the tension of the shutter spring and means for adjusting the slit width.

In the drawings, 20 is a base plate suitably contoured to act as a support for the operating parts of the camera and for a housing or housings to enclose the same. The latter have not been shown in the drawings, but the lens and the bellows (or other type of light proof exposure serving the same purpose) have been shown in broken lines at 2! and 22, respectively, (see Fig. 1). The base plate 20 is generally flat with bosses and depressions where needed for thesupport or accommodation of the various parts, and is shown with a flange 23 running around its rim, to which the aforementioned housings may be conveniently secured.

Slidably mounted in the base plate is a bar 24, on which is carried a structure functioning as a pressure plate and a support for the shutter. This bar also has connected to it the lens proper and its focusing mechanism (not shown). This structure comprises a plate-like member 25 having an extension 26 at its base which is secured to the bar 24 by screws 21, and which is provided with an aperture 28 positioned at the inner end of the bellows, and through which light from the lens 2| passes through the shutter, and through a corresponding registering aperture 25 in a pressure plate 30, which is carried on the member ll, being secured thereto by screws 3|.

Immediately to the rear of the pressure plate is positioned a film 32, shown in broken lines in Fig. 1, and this is guided over rollers 33, passing from a spool 34 to a spool 35, which latter is the take-up spool, these parts also being shown in broken lines in Fig. l. The spool 35 is adapted for coupling to a stub shaft 38 which carries a pinion I! (see Fig. 10) serving to actuate the shaft 35 and thereby the take-up spool II, by mechanism to be hereinafter described. The stub shaft 38 is journalled in the base plate 20 and in an extension 38 of a bracket "which is secured to the base plate by screws 40 and which serves for the support of the Shutter releasing trigger, as will also be described hereinafter.

A pair of brackets 4| and .42 extend rearwardly from the upper and lower portions, respectively, of one side of the member 25 (see Figs. 1 and 3), and serve for the support of a pin 43 on which is journalled a reel 44 provided with flanges 45 at its ends and serving as one of the supports for a shutter curtain 46.

The curtain 46 is a sheet of thin non-stretchable material held in the form of an endless band by means of a pair of tension coil springs 41 and 48 which pass completely around the curtain as clearly shown in Figs. 1, 2, 5 and 9, and have the ends of each secured to opposite ends of the curtain. .By using this arrangement, rather than connecting the opposed ends of the curtain directly by short lengths of spring, it is obvious that a wide range of adjustment of the space between the ends of the curtain or slit width is obtainable without exceeding the elastic limit of the springs. The manner of attachment of the springs is shown in Fig. 9 of the drawings wherein 49 and 5| are ends of the spring 41 which are connected, respectively, to hooks 50 and 52 carried respectively, by reinforced ends 53 and 54 of the curtain 45.

Ends 55 and 56 of the spring 48 are similarly secured to hooks 51 and 58 positioned, respectively, on the reinforcedportions 53 and 54.

A second curtain-supporting reel 59 is journalled on a pin 68 mounted in a U-shaped bracket H (see Figs. 1, 3 and 4), which is mounted for pivotal movement about a vertical axis passing through an intermediate point in upper and lower arms, 62 and 53, respectively, on brackets 54 lower portions ofthe other side of the member 25.

The reel 59 is similar to the at the top and the bottom 46 on the reel.

The arm 62 of bracket pin 81 secured thereto as by set arm 5?. of said bracket with a pin 69 also secured thereto by means not shown, and these pins are iournalled in the aforementioned brackets 64 and to retain the curtain Giis-provided with a 65 to provide the pivotal mounting for the brack- Y et I. Since the pin 80 is mounted-at the ends of the arms 62 and 83, while the bracket 8| pivots about the pins 61 and 69 at same distance inward, it will Fig. 1, results in a movement of the reel 50 away from the reel 44. I from the broken line to the full line position results, of course, in an approach of the reel 58 to the reel 44.

The effect of this variation of the distance between the curtain-supporting reels on the width of slit 10 of the shutter will be made clear with the aid of Fig. 5, which is diagrammatic in charends of the curtain 46 as shown in full lines, and

this distance may be represented with sufiicient accuracy for the purposes of this demonstration by the ditsance a in Fig. 5. When the reel I! is moved into its. broken line position, however, the

curtain will move with it and its ends will move away from their full line positions into their broken linepositions, so that the width of the slit is now approximately represented by b in Fig. 5. It will be observed that the increase in the width of the slit is equal to twice the increase in the distance between the reels. In other words, if this distance is (see Fig. then C=/g(bfl).

Spacing bushings H and I! on the pin I serve to keep the reel 59 at the proper level in alignment with the reel .44. Suitable means (not shown) may be provided for adjusting the position of the bracket 6| from the outside of the camera.

This means may be in the form of a control attached to the bracket ii at an extension 12a thereof (see Figs. 3 and'4);

By reference to Fig. 1 it will be noted that the curtain 46 is guided in frontof the pressure plate 30 and in the space between the front wall of the member 25 and the pressure plate, and thatthe springs 41 and 48 are also accommodated in said space, which is bounded atits top by a flange" extending rearwardly from member 25 and at its bottom by a flange I4, also extending rearwardly from said bracket (see Fig. 3), these flanges servscrew '68, and the" be seen that pivotal movement of the bracket 6i, such as indicated in brokenlines in Movement oi. the bracket 6| cated by the arrow 16a in reel 44, being of the same size and being provided withfianges 66 l 'pin 4! to a gear 4!.

shutter will travel through one complete cycle, 3 which is terminated by the 'end 18 of lever 19.

pin 18 striking the The impulse lever 19 is pivoted at an inter mediate point thereof to a boss I of the base plate 2| (see Figs. 8 and 9) by means of a screw Ii, which also serves as the pivot for a setting lever ",the free end of which is pivotally connected by a screw bite one end oi a link 84, the other end ofwhich is pivotaliy connected by a The end portion striking end, has already been described. In order to perform its function eflectiveiy with a minimum of noise and jarring, its striking portion'is preferably padded as by a stripor strips I! of leather or thelike secured to the end ll of the lever so as to form a thickened pad. The lever It, as most/clearly appears from Fig. 8,

is of flat material disposed horizontally for the most part, The portion 18, however, is vertically disposed, whereby it serves as a latchadapted to enter a notch 88 in the end of a trigger lever 83.

The lever 00, the contours of which need not be described since they are clearly disclosed in Figs.'1, 2, 8 and 10, is pivoted at an interme diate point thereof, on the bracket a, previously mentioned. This bracket, while is secured to the base plate 20, is provided with a pair of ears ti and 8| into the opening of which extend lugs 92 (see Figs. 2 and 8) whichextend laterally from the lever N. The pivotal mounting may be adjusted by set screws 93 (see Fig. 2) on which the lugs 92 rest, and the throw of the lever may be regulated by a set screw .4 ends nut 95.

The notch B8 is positioned on one leg 90 of the lever 89', which may be termedithe latch-engaging end of the lever. Its other leg I! which may be described as the operating or control leg,

. is bent angularly. Its free end 88 may serve for the attachment of a suitable control device leading to the exterior of the camera housing, such as a push button, for instance.

The operating leg 91 is normally urged into a raised position and the latch-engagingleg II is ing for the support of the pressure plate 30, as

already described, being provided with bosses 15 to receive the screws 3!. I 7

By reference to Fig-1 it will be further noted.

that the slit it! is located at the right hand side, overiying the reel 45, this being its initial position which is determined by a stop in the form of a pin 16 supported on a bracket ll suitably se cured to the curtain 46.

correspondingly urged into a depressed position by a spring 89, which is in the form of a leaf springlhaving one end doubled over and interposedbetween the leg 98 of lever I! and the base plate 20. This spring is shownin its entirety in Fig. ,8.

The motive power for the curtain is provided by a coil spring I" which is attached at one end to a lug Ill on the end of a leg ill of impulse lever 19. The other end of the spring I" isattached to the bracket ii at a point I re moved from its'pivot. Due to this connection of the spring, it is obvious that when the bracket Si is moved so as to increase the distance between the curtain carrying reels 44 and 5!,

which will have the effect ofwidening the slit 10, the tension on the spring in! is decreased, and this decreased tension will result in a less forcible impulse given to the curtain by the lever 19 when it moves under the action of said spring after its latch portion 18 is released from the notch 88 of the triggerlever 89, thus increasing the lengthof the exposure. a

While this construction represents a preferred described hereinafter, and its 78 of the lever, which'is the form, it is to be understood that, if desired; the tension of the spring and the spacing of the reels may be independently adjusted by suitable control means provided therefor.

The setting of the shutter is effected by means of a lever or crank I04, having a handle "4a, secured to a pin or stub shaft Ill! iournalled in a pocket Hit. of the base plate 2!. The upper end of the shaft I" has a cam I" fixedly se cured thereo, while the gear it, already referred to hereinabove, is mounted for free movement on the shaft I and underneatif the cam Ill. The latter has a slot llil into which projects a pin lb! on the gear 8, whereby the movement of the gear relative to the cam is restricted.

The cam is further provided with a slot HI into which extends a pin HI carried by the bar i i, The slot is contoured to cause an advance of the bar 24 in a forward direction, as indicated by an arrow H2 in Fig. 10, whenever the crank M4 and the cam ii! are moved in a clockwise direction, as indicated by arrows H3 and H4 in Fig. 10. Once the bar 24 is in its forwardly advanced position, it is prevented from moving back by a concentric edge portion III of the cam II! which engages the pin Ill on continued rotation of the cam I". On the other hand, forward movement of the lever beyond the sphere of action of cam M1 is prevented bythe rim 2! of thebase plate, a portion of which acts as a stop for pin ill which will keep it from traveling outside of the path of a projecting nose portion iii of the cam I".

A recess ill in the cam Ill accommodates pin 85 under certain conditions.v

The system of links and levers for setting and operating the shutter, and which is shown in Fig.8 in perspective has already been described. This description will be completed by mention of an upstanding lug ill on the setting lever II. which serves to engage and move the lever ll Whenever lever 82' is moved by link 04 as a result of the movement of gear I. The connection of the link 84 to gear I. by the pin II has already been mentioned; at III in Fig. '1 is shown an opening to receive the end of this pin II,

An end portion H! of the leg 90 has a lower edge I20 inclined upwardly so as to serve as a cam surface which will ride on the upper edge of the portion 1! of the impulse lever II, whereby, as the said portion is moved, the leg it will be raised against the tension of spring I! until the portion 18 enters the notch 88, when the spring 99 will act to depress the leg 46 and prevent the portion I8 from leaving the notch until the leg 96 is raised, as by manually depressing the end 88 of the lever 89.

The operation of the device will now be described:

After operation of the shutter the parts thereof will be in the position shown in Figs. 1, 2, 4, 8 and 10 with the pressure plate 3| pressing against the film 32 and the pin I. to the left of the pad 81' of the end 18 of impulse lever ll, and said end 18 being free of the notch ll of the trigger lever 89, while the crank I04 will be in the position shown particularly in Figs. 1 and 10. The position of the cam Hi1 and the gear 86 appears from Fig. 10. The arm 6! is shown for purposes of illustration in its position of minimum slot width. The spring I" has pulled the leg I02 of impulse lever 19 against the lug ii! of lever 82; the latter acts as a atop because it is prevented from moving by the link 84, which in turn is prevented from moving by the gear 10, that is clockwise, and the cam Ill moves clockwise in the direction of the arrow III. This movement of the crank I44 is continued until the position of the parts shown in Fig. 11 is reached after which farther movement of the crank in a clockwis direction may be prevented by suitable stop means (not shown).

The first result of the movement of cam III is that it moves bar 24 forward, because of the action of cam slot Ill on pin I carried by the bar 14. This carries the member II with the curtain and its reels forward and serves to disenssse the pressure plate 3| from the film 12. Until this disengagement is eifected, the gear I! h'asbeenidlingbecauseits pin Illisfreeto travel in the cam slot Ill until the end of the cam alot I" engages the pin and causes the gear 84 to move with it. When this happens, the pressure plate ll has released the film I2 and the latter is now unwound for a fresh exposure by the action of gear II on the pinion 3!, which through shaft 3. drives the take-up spool II. At the same time the gear It moves link 44 and thereby sets lever 82 in a clockwise direction. and the lug I of lever 82 presses against leg III of the impulse lever ll, causing said lever to move into the position shown in Figs. 11 and 12, in

which end 18 of lever 19 has entered the notch ll of the trigger lever-ll, where it has become locked. It is now situated to the left of pin II. This movement of the pad ll on the end of part II is possible because the bar 24 has moved the reel 44 forwardly to such an extent that the pin 14 is clear of the path of pad 8 The spring Ill is under tension and ready to actuate the lever II when it is released.

The crank III is now moved in the reverse direction, that is in the counter-clockwise direction indicated by arrow in in Fig. 11, until it reaches its starting position again, as shown in Fig. 13. All of the parts, except the lever II and the spring I", move back to their starting position of Fig. 10 with the crank I. The lever ll remains in its latched position in notch ll of trigger lever 89, and the spring I" is under tension.

It will be observed that the bar 24 has moved back into its initial position carrying with it the curtain heels 44 and II, so that now the pin 10 is again in the path of the pad 18 of lever 1!. Now, however, the pin 16 is to the right of the pad 81, instead of to the left thereof, as in Figvv 10. The pressure plate I. also again presses against the film.

It is to be understood that the transmission between the shaft 38 and the 111m take-up spool 36 is unidirectional so that during the movement of the gear N from the position of Fig. 11 to that of Fig. 13 the film is not moved.

Operation of the shutter is effected by raising the end ill of trigger lever US, as by depressing its control end II, which releases the lever 10. This lever, under the action of spring I gives an impulse to the curtain 44 in a counter-clockwise direction, as indicated by the arrow Ila of Fig. 1, and-the slit IO travels at substantially uniform speed across the apertures 28 and 2!,

thereby exposing the film 31.

The curtain 4i continues its movement at substantially uniform speed until the pin 16 strikes ll at the end the pad :1, which causes it to rebound into its initial position as shown in Fig. 1.

In order to cause the pin 1 always to retum I proper always returning to the same place around the outer curvature of the reel 4|.

."It will be understood that any suitable or preferred material can be used for the various parts. For the base plate and the member ii I have found aluminum satisfactory. The curtain 48 may be made of very thin sheet steel or spring hard phosphor bronze or nickel silver. The springs 41, 48 and I" may be made of thin steel wire. 7

It is obvious that many changes of form, proportions and minor details of construction may be resorted to without departing from the principles or sacrificing any or the advantages of the invention as defined in the appended claims.

What I- claim as new, is:

1. In a focal plane shutter for cameras, a curtain, anti-friction supports for said curtain, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exp sure.

2. In a focal plane shutter for cameras, an endless belt forming a curtain, anti-friction supports for said curtain, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said ourtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure. Y

3. In a focal plane shutter for cameras, an endless belt having an adjustable slit forming a curtain, anti-friction supports for said curtain, and mechanism to impart an impulse to said ourtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

4. In a focal plane shutter for cameras, an endless belt forming a curtain, a pair of reels having said curtain wound around it, anti-friction supports for said reels, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member'upon release and being disengaged from said member during exposure. 5. In a focal plane shutter for cameras, 9. ourrain assembly consisting of an endless belt having an'adjustable slit forming a curtain, a pair of reels having said curtain wound around it, anti-friction supports for said reels, and means to vary the distance between said reels for purposes of varying the width of said slit, and mechanism to impart an impulse to said curtain assembly, prior to exposure, to operate said assembly by its own inertia only during exposure, comrising a spring actuated member and means to release said member, said curtain assembly having'a contact surfac adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

6. In a focal plane shutter for cameras, a curtain having ends in spaced relation to each other forming a slit, elastic means connecting said ends formihg an endless belt with said curtain, a t friction supports for said curtain, and mechanism to impart an impulse to said curtain, prior to exposure, j'to operate "said curtain by its own lnertiaonlyi'during' exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

7. In a focal plane shutter for cameras, a cur tain having ends in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pair of reels having said curtain wound around it, anti-friction supports for said reels, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member 1 upon release and being disengaged from said member during exposure.

8. In a focal plane shutter for cameras, a curf tain having ends in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pair of reels having said curtain wound around it, said elastic means passing around said reels, antifriction supports for said reels, and mechanism to impart an impuls to said curtain, prior to ex posure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure. 9. In a focal plane,shutter for cameras, a curtam having ends in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pair of reels having said curtain wound around it, said elastic means passing around said reels, anti-friction supports for said reels, means to vary the distance between said reels for purposes of varying the width of said slit, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own in-' ertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

l0. In a' focal plane shutter for cameras, a curtam, a pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate ofi said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to 0perate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

11. In a focal plane shutter for cameras, an endless belt forming a curtain, a pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate off said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

12. In a focal plane shutter for cameras, an

endless belt having an adjustable slit forming a curtain, a pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate on said film during rewindlng, and mechanism to impart an impulse to said curtain,'prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

13. In a focal plane shutter for cameras, an

endless belt forming a curtain, a pair of reels having said curtain wound around it, a pressure plate for film cooperating with said curtain'and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate off said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

14. In a focal plane shutter for cameras, an

endless belt having an adjustable slit forming a curtain, a pair of reels having said curtain wound around it, means to vary the distance between said reels for purposes of varying the width of said slit, a pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate off said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

15. In a focal plane shutter 1'01 cameras, I. curtain having ends in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate off said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

16. In a focal plane shutter for cameras, a curtain having ends in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pair of reels having said curtain wound around it, a

pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate oil. said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising I. spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said member upon release and being disengaged from said member during exposure.

1'7. In a focal plane shutter for cameras, a cur tain having and: in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pair of reels having said curtain wound around it, said elastic means passing around said reels, 8 pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate off said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surfape adapted to ,receive the impulse of said member upon release and being disengaged from said member during exposure.

18. In a focal plane shutter for cameras, a curtain having ends in spaced relation to each other forming a slit, elastic means connecting said ends forming an endless belt with said curtain, a pair of reels having said curtain wound around it, said elastic means passing around said reels, means to vary the distance between said reels for purposes of varying the width of said slit, 8, pressure plate for film cooperating with said curtain and movable in unison therewith in a direction parallel to the optical axis of the camera lens, means to lift said plate on said film during rewinding, and mechanism to impart an impulse to said curtain, prior to exposure, to operate said curtain by its own inertia only during exposure, comprising a spring actuated member and means to release said member, said curtain having a contact surface adapted to receive the impulse of said memberupon release and being disengaged from said member during exposure.

ALFRED SIMMON. 

